WPF Combobox Select 名称使用ID

Question

I have a ComboBox , and I am trying to use names in it, but when the user selects a name, I want to select an ID instead of the name.

Here's my XAML:

<ComboBox x:Name="cb_tvrtkaID" Height="25" Margin="0,10,0,0" Loaded="cb_tvrtkaID_Loaded"/>

And my C#:

private void cb_tvrtkaID_Loaded(object sender, RoutedEventArgs e) {
    MSSQLConnect sql = new MSSQLConnect();
    bool sqlIsConnected = sql.Connect();
    string query = "SELECT tvrtkaId,tvrtkaNaziv from sifarnik.tvrtka";
    SqlConnection connection = sql.GetConnection();
            
    if (connection != null) {
        using (connection) {
            try {
                SqlCommand cmd = new SqlCommand(query, connection);
                SqlDataReader reader = cmd.ExecuteReader();
                    
                if (reader.HasRows) {
                    while (reader.Read()) {
                        cb_tvrtkaID.Items.Add(reader["tvrtkaNaziv"].ToString());
                        //cb_tvrtkaID.Items.Add(reader["tvrtkaId"].ToString());
                        cb_tvrtkaID.SelectedItem = reader["tvrtkaId"].ToString();
                        cb_tvrtkaID.DisplayMemberPath = reader["tvrtkaNaziv"].ToString();

                    }
                }
            }
            catch (Exception ex) {
                Debug.WriteLine(ex);
            }
        }
    }
}

This gives me the following error:

System.Windows.Data Error: 40: BindingExpression path error: 'Arbet-grad d' property not found on 'object' ''String' (HashCode=-1526763463)'. BindingExpression:Path=Arbet-grad doo; DataItem='String' (HashCode=-1526763463); target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')

System.Windows.Data Error: 40: BindingExpression path error: 'Arbet-grad d' property not found on 'object' ''String' (HashCode=1553220975)'. BindingExpression:Path=Arbet-grad doo; DataItem='String' (HashCode=1553220975); target element is 'ComboBox' (Name='cb_tvrtkaID'); target property is 'NoTarget' (type 'Object')

How can I resolve this error, so that a name is displayed but the underlying ID is selected?

Answer 1

In general, what I would suggest is to populate your combobox with objects that contain name and ID. Then configure your combobox to show the name of the object.

 <ComboBox x:Name="cb_tvrtkaID" Height="25" Margin="0,10,0,0" Loaded="cb_tvrtkaID_Loaded">
       <ComboBox.ItemTemplate>
               <DataTemplate>
                   <TextBlock Text="{Binding Name}" />
               </DataTemplate>
       </ComboBox.ItemTemplate>
   </ComboBox>

The objects in the combobox would be defined by:

  class cbItem
   {
      public string Name{get;set;}
      public string ID;
      public cbItem(string name, string id)
      { Name=name; ID=id;}
   }

And in your code, you would add the items like:

 //[...]
   while (reader.Read())
      {
         cbItem myCbItem = new cbItem(reader["tvrtkaNaziv"].ToString(), reader["tvrtkaId"].ToString();
         cb_tvrtkaID.Items.Add(myCbItem );
         
         //from outside this method, you can find the item of your combobox whose ID property is x, simply by iterating or with the help of Linq
         cb_tvrtkaID.SelectedItem = myCbItem;
      }

//[...]

Don't forget to clean the combobox items every time that you load from the SQL using cb_tvrtkaID.Items.Clear() .

You can accomplish the same results above using a binding to a list of cbItem s and a converter, for example